To understand the fundamental principles of the Hall effect, an international team, in collaboration with researchers at IRIG, has succeeded in bending the path of atoms using laser light. More conventionally, the Hall effect deflects electrical charges in conductors, enabling it to be used as a technique for characterizing materials and measuring the magnetic fields of our domestic appliances, such as cell phones. ​​

For 40 years, the behavior of particles subjected to a magnetic field, when their interactions become strong, has remained a mystery. Recent theoretical work, carried out by teams at Irig and the University of Geneva, has predicted the remarkable behavior of these systems. Now, the experimental team at the University of Florence, in collaboration with theorists at IRIG, CNRS and the University of Geneva, has used a quantum simulator - a quantum computer "dedicated" to a specific task - to confirm this theory experimentally. It studied in real time how a jet of atoms bends under the effect of a magnetic field, something that had never been observed before: cooled to the extreme of a few billionths of a degree above absolute zero, neutral atoms behave like electrons. By irradiating the atoms with laser light, the researchers were able to describe precisely how their trajectories bend in the presence of an "artificial" magnetic field, just as charged particles would (cf. photo 1).

​​​​Photo 1: ​​Details of the laser experimental setup © Carlo Sias.

Thus, confirming theoretical predictions for the first time, the Hall effect was measured by varying the interactions between the particles (cf. Figure 2).

​​ Figure 2: Observation of the Hall effect on strongly interacting fermions (courtesy of the journal Science).​

​These promising results would finally elucidate the microscopic origin of the quantization of the Hall effect, which, 40 years after its discovery, remains in search of a complete theoretical interpretation. This research will continue as part of the National Recovery and Resilience Plan (PNRR) initiatives dedicated to the development of new quantum technologies.